I'm trying to drag and drop (slide) a Silverlight element from one part of a window to another.
I've implemented the MouseLeftButtonDown, MouseMove, and MouseLeftButtonUp event handlers on the element, but I've run into a bit of a problem.
All of the examples I've seen involve moving the element by setting the Canvas.Left and Canvas.Top properties. None of the elements I'm trying to manipulate live inside a Canvas. Is there a way to set the absolute position of the element being dragged, based on the coordinates of the mouse? Or is there a prepackaged solution to this problems somewhere that I've missed?
All panels but Canvas use some kind of constraint to position their children. Only Canvas lets you use absolute positioning. That's why I think it is the only way to implement drag and drop .
Feel free to use a Canvas on top of your existing panel. Just remember to remove the dragged element from its original parent and put it in the Canvas (or drag some kind of copy) and do the reverse on mouse up.
One way of achieving absolutely positioning an item inside any container, not only Canvas, is to use transformation instead of Left/Top properties. For instance, to set at Left=50 Top=80 you can modify the margin values through transformation.
Related
I have a Rectangle nested within a Canvas. The rectangle has a MouseDragElementBehavior attached to it, so it can move freely in the canvas.
I need to calculate the position of the rectangle after each drag. The problem is that the
Canvas.GetTop(rectangle1)
only works for the first time, i.e. before the rectangle is dragged. After the drag, the method call returns the initial position.
Those behaviors usually work by applying a RenderTransform, if it uses a TranslateTransform you can get the offset value from that and add it to the canvas position.
Alternatively you might just want to implement your own dragging logic.
I have some problems with implementing autoscrolling in WPF (I think I could call it that way).
I have a canvas placed inside a scrollviwer. On my canvas I can dynamicly add different shapes. The position of this shapes can be changed with mouse. Everytime I add new shape on canvas or change position of shape I fire measureOverride function.Thanks to this scrollview "know" the real size of canvas and the scrollbars appear. However even if scrolbars appear, the view doesn't "follow" shape which I currently move. I mean if I reach visible part of canvas I would like canvas to srcoll.
I was trying to use this function
ScrollToHorizontalOffset()
However I have problem with proper use of that function. I was trying to use (as a parameter) canvas actualwidth but it didn't work well. I also was trying to use as a parameter current position of shape (which I move) but it works only one way. I the viewer follow the moving element if I was moving this element to right side of canvas. However if I move shape back(to the left) the view don't follow the shape.
I hope somebody will understand this :) It is hard to explain my problem.
I also was trying to use as a
parameter current position of shape
That is the correct way to implement. Waht you need is a converter, which will returns the position according to the direction you move the object.
I have stack panel with custom controls in it. User can add or remove the items.
I have attached MouseDragElementBehavior to each item. So now user can move them within the stack panel.
However the items now are arranged on arbitrary manner. Is a mess really. They stay where the user left them.
What I need now is to make them to be stacked as the stack panel supposed to be... Nicely one by one...
So I need to simply let user change the order of items by using drag / drop operation but items has to be stacked precisely.
There is DragFinished event, but I dont really see how the Behavior moves items. I thought it is Margin it changes but margins stays 0... I dont know what to do next.
Appreciate little help.
MouseDragElementBehavior does its work using a Transform on the RenderTransform property of the attached element (i.e. the one the behavior is applied to) (the exact type of transform depends on the state of the RenderTransform property but it will either be a TranslateTransform or a MatrixTransform).
The transform is not reset when you finish dragging (nor would you want it to be because the element would snap back to its position in the StackPanel when you started dragging) and this is why the element stays where "the user left them".
To change the items position in the StackPanel in the way you are talking about you will have to use the DragFinished event. What you probably want to do is work out where in the StackPanel the element will end up (as a result of the drag, i.e. which element in the panel it will "push" down) then create an animation to animate the element from its current position (where the user released the drag) to that final position in the StackPanel and another animation to move the "pushed" element in to its new position in the StackPanel (VisualTreeHelper can probably help here (I think)). Once those animations are finished just set the new index within the StackPanel for each item and remove the RenderTransform translation.
I've got a container, say a Grid. It has two containers, say StackPanels.
StackPanel #1 has some rectangles. What's the best way to enable a user to drag a rectangle and drop it in the StackPanel #2 (and have that rectangle be a child of StackPanel #2).
I've got the drag bit sussed - the only thing that's unclear is whether to actually use containers or just handle all the rectangles manually in a straight canvas.
As far as the logic behind actually moving the items goes, a StackPanel as a container is just fine. If you want to preview the item whilst it's being dragged, you can implement an Adorner that displays the Visual whilst it is being dragged.
I like to use a grid to position some objects in WPF, because it cares about the position and stuff. In addition, however I also like to be able to draw accross the cells with a Canvas.
I figured out that this can be done by embedding the grid in a canvas. However in order to connect two elements, I need then the absolute position in pixels.. any ideas?
From code you can use the UIElement.TranslatePoint() method.